The present invention relates to a method for joining a plate chain link, wherein at least one plate is connected to at least one bolt by a pressing and aligning process. Furthermore, the present invention relates to a method for carrying out the method.
In the prior art very different methods for joining a plate chain link or a plate chain have established themselves. These methods are in part quite different and are adapted to the designs of the various plate chains. There are methods in which only the inner chain links are produced and a further method is subsequently performed for joining the chain by producing the outer chain links, with the already prefabricated inner chain links being interposed. This means that the methods must be suited, on the one hand, for joining solid bolts with plates and, on the other hand, for joining hollow bolts (sleeves) with plates. In the manufacture of an outer chain link for a duplex chain a plate must e.g. first be slid in central fashion onto a solid bolt. The interposition of rollers for making a roller chain should also be possible with the individual methods.
In particular in high-quality control chains, dimensional accuracy with respect to the parallelism of the bolts (solid bolts and sleeves) and plates, the distance of the plates when several plates are used, as well as the centering of the chain link elements relative to the main chain axis, are of decisive importance.
Normally, the chain links are built up from below. This means that the lower plate is first positioned and the associated bolt is supplied. In the manufacture of an inner chain link the plate and the sleeve are then centered relative to each other via a positioning mandrel projecting from the assembly plane. Subsequently the lower plate and the sleeve are pressed together. Optionally, before or after said process a roller may additionally be mounted on the sleeve. Finally, the upper plate is supplied and also centered relative to the sleeve by means of a positioning mandrel and subsequently pressed thereonto. This procedure is carried out at predetermined cycles so that a joint press block operating with a specific lift number respectively applies the pressing force. This can be carried out on a circular table or successively in series.
DE 2 457 241 A1 already discloses a method for producing chain links on successively arranged rotary mounting tables, the method employing the layered construction of the chain link from the bottom to the top, but already effecting an excellent alignment of the individual chain link elements relative to one another thanks to the skillful use of positioning mandrels. This method, however, employs many joining steps which must be simplified. Moreover, a centering relative to a main chain axis is not fully achieved. What poses, in particular, problems are the different lengths of the bolts, so that the centering operation relative to the main chain axis is not satisfactory. It is now desirable to provide a method which with a few steps can achieve an adequate centering or symmetry of the chain links to be produced relative to the main chain axis, i.e., independently of the type of chain link (by centering a single plate in the center of the bolt or by symmetrical arrangement of two plates on the end portions of a bolt).
It is therefore the object of the present invention to provide a method and a device for joining a plate chain link which exhibits improved dimensional accuracy, in particular, with respect to symmetry in relation to the main chain axis.
According to the invention this object is achieved by providing a method for joining a plate chain link of the above-mentioned type, in which the at least one bolt is centered relative to a main chain axis by the simultaneous active application of symmetrical clamping forces to the faces of the bolt, and the at least one plate is pushed by a joining lift relative to the bolt into a position symmetrical to the main chain axis on the bolt.
The method of the invention mainly differs from the methods in the prior art by the features that while the bolts are being centered there is no action against a fixed stop, but rather a central centering operation is carried out by the simultaneous application of symmetrical clamping forces. Of particular importance is here the term xe2x80x9cactive applicationxe2x80x9d because in the prior art the force is actively applied only from one side, whereas the other side in this process is at a standstill and acts as a stop (passive application of force). The difference is now that in the prior art the dimensional accuracy, in particular, of the symmetry relative to the main chain axis is determined by the face of the chain bolt that rests-on the stop. In the present invention, the center of the main chain axis is always found in an exact way because the bolt is automatically aligned with said axis due to the active application of symmetrical clamping forces. The principle is similar to a pair of tongs in the case of which the press forces are also applied in symmetry with a line of symmetry extending through the pivot axis of the tongs. The advantage is that the chain bolts need not necessarily be produced with a very small range of tolerance, because the faces of a bolt always have the same distance from the main chain axis. This makes it also possible to simultaneously center the two bolts of a chain link in one operation if these are respectively acted upon with symmetrical clamping forces. It might be that a distinction has to be made in this method between joining lift and centering by the symmetrical clamping forces because an excellent dimensional accuracy (symmetry) is also achieved when the symmetrical clamping forces become only operative at the end of the joining operation and thereby ensure the final joining position of the bolts.
In most cases it is of advantage when the joining lift is carried out by pushing the at least one plate onto the at least one bolt and by moving the at least one plate by the simultaneous active application of symmetrical joining forces into a position in symmetry with the main chain axis. In this instance, too, the force may only be applied during the joining lift at one side of a plate as long as it is ensured that a symmetrical force couple is applied at the end of the joining lift to arrange the plates in symmetry or to center the one plate in the center. By analogy with the bolts, the plates are then also very exactly aligned relative to the main chain axis.
Furthermore, it is also possible for specific chain links that the joining lift is carried out by pushing the at least one bolt into the at least one plate and that at least at the end of the joining lift the at least one bolt is centered relative to the main chain axis by the simultaneous active application of the symmetrical clamping forces. This means in such a case that the plates are not pushed onto precentered bolts, but the at least one bolt is pushed into an opening of the plate and the bolt is subsequently centered. In such a process the plate can be fixedly anchored in its position. Such a procedure is mainly applied in the case of intermediate pin plates for duplex chains because in duplex chains the push-on paths of the bolt relative to the plate are bound to be long.
When two plates are simultaneously pushed onto the respectively opposite end portions of the bolt, this may be carried out via a corresponding centering stop on the force-applying elements, so that these occupy their symmetrical position relative to the main chain axis. Each of the outer surfaces of the plates will then have exactly the same distance from the main chain axis. Since the thickness of the plates can be produced at the same costs with a much smaller tolerance than the length of the bolts, the distance of the insides of the plates is also within the necessary range of tolerance.
Advantageously, a further method step may be provided in which the at least one plate and the bolt are prepositioned relative to one another so that an opening in the plate is arranged to be coaxial to the bolt. What should here also be called novel is the fact that independently of the number of the bolts and the plates the whole chain link can be prepositioned and can be joined in a joint centering and pressing operation. This, however, means that, in contrast to the prior art in which many lifting operations were needed for joining a single chain link, these can be carried out in a single joining station thanks to the method of the invention. On the one hand the pressing operation proper can be performed at a lower speed so that advantageous pressing conditions with less heat development are prevailing. On the other hand, the number of the manufactured parts can nevertheless be at least maintained if not even increased per time unit.
Furthermore, it may be provided that simultaneously with the application of the symmetrical clamping forces the at least one plate is guided to be coaxial to the bolt and is already pressed in part onto the bolt. As a result, the plates are centrally attached to the bolt so that no additional attaching forces have to be applied by the joining lift proper.
To apply the symmetrical clamping forces in a way that they are as coaxial to the bolt axis as possible, these can be produced by two positioning mandrels that are movable towards each other in a uniform and constant way. While the centering operation is carried out by the positioning mandrels themselves when hollow bolts are used in the case of an inner chain link, it is possible in the centering operation of a solid bolt to hold said bolt in portions in a prism for aligning the same in coaxial fashion. Such positioning mandrels can also be guided very easily and can accurately be attached to the bolt.
To enable the joining lift to apply a pressing power which is distributed as uniformly as possible around the bolt axis, the joining lift may be carried out by an upper and/or lower press block arranged around the positioning mandrels, with the press blocks applying the symmetrical joining forces. Since the positioning mandrels normally have a diameter substantially corresponding to (most of the time slightly smaller than) the outer diameter of the. bolt, the press block additionally provides a guide when the plates are pressed on. This is of enormous advantage in particular when a single plate is pressed into the center of a long bolt in a duplex-type outer chain link because the long bolt cannot deflect. It is again important that the joining lift can only be carried out by one press block when a single plate is pushed on and that the plate is aligned at the end of the joining lift by a counterpressure of the second press block.
Optionally, it may be desired that the joining lift is carried out by a positioning mandrel and that the symmetrical clamping forces for a bolt are applied by positioning mandrels that can be moved towards each other in a uniform and constant manner. This means that a bolt (sleeve) is pressed into a plate by means of the positioning mandrel and that a centering operation is only carried out at towards the end of the joining lift by the action of the second positioning mandrel from the opposite side.
Furthermore, the present invention relates to a device for joining a plate chain link. The device comprises an axially movable upper positioning mandrel and an axially movable lower positioning mandrel between which a bolt of the chain link can be positioned and clamped, a lifting mechanism by which the positioning mandrels are displaceable at a right angle relative to a main chain axis and by which active symmetrical clamping forces in relation to the main chain axis can be applied to the faces of the bolt, so that the bolt can be centered relative to the main chain axis, as well as an upper press block and a lower press block by which the at least one plate can be brought into a position in symmetry with the main chain axis or can be clamped therein.
The device is constructed such that it centers the at least one bolt of the chain link in one joining operation and pushes the at least one plate onto the bolt. The bolt can also be pushed into the plate. Furthermore, it is novel that a positioning mandrel is used for applying a clamping force. Positioning mandrels that have been used so far have mainly been used for coaxial alignment and not for the application of axial forces. In this respect it would be possible to produce a joining head according to such a principle, with the head producing a chain link by means of a single joining operation, or finishing a chain by assembling an outer chain link with interposition of an inner chain link. The alignment relative to the main chain axis forms part of the joining operation. The lifting mechanism must have a symmetrical forced coupling of the positioning mandrels. This forced coupling may also be carried out hydraulically, or pneumatically, but preferably mechanically. A principle based on some kind of tongs is here possible as a simple means of solution.
According to an advantageous development a lifting mechanism may be provided for displacing the upper and lower press blocks, by which lifting mechanism said press blocks can be displaced in symmetry with and at a right angle to a main chain axis and by which, at the same time, active symmetrical joining forces in relation to the main chain axis can be applied for performing the joining lift, so that the at least one plate can symmetrically be pushed onto the bolt. Depending on the construction of the chain link, this may be the same lifting mechanism as used for the positioning mandrels. In most cases, however, a separate lifting mechanism which is arranged in parallel therewith is used because the press blocks have to be actuated in a different way than the positioning mandrels. At any rate, this preferred and also force-coupled lifting mechanism provides for an adequate symmetry of the plates on the bolt.
In particular for the production of an intermediate pin plate for a duplex chain, the press block in a simplified version of the device may be designed as a movable and a stationary clamping jaw by which the at least one plate can be fixedly clamped in a position substantially in symmetry with the main chain axis, and the joining lift can be carried out by the at least one positioning mandrel. The press blocks are adjusted such that the plate can be clamped substantially in symmetry with the main chain axis between said blocks. In such a case the plate does then not perform a further aligning movement during the joining operation. The bolt is slid into the plate at one side and at the end of the joining lift it is centered by the symmetrical application of the clamping forces in symmetry with the main chain axis.
Advantageously, the lifting mechanism for the two positioning mandrels may comprise a joint drive with forced guidance, by which the two positioning mandrels are movable in coaxial and symmetrical fashion relative to each other. The lifting mechanism is thereby strongly simplified because a single drive moves both positioning mandrels. A forced guidance will then provide for the symmetrical conversion of the displacement path predetermined by the drive and of the displacement speed.
The lifting mechanism for the upper and lower press blocks may also comprise a joint drive with forced guidance by which the two press blocks are movable in coaxial and symmetrical fashion relative to one another. The same advantages as for the joint drive of the positioning mandrels are here observed.
When according to one embodiment the drive comprises a slide bushing which is controlled in its linear movement by a cam and which moves the positioning mandrels or the press block via a symmetrical lever linkage, it is additionally possible to combine the drive for the press blocks and the drive for the positioning mandrels because the two cams can be jointly drivable. The guidance by means of cam and controlled slide bushing is very robust and can apply the necessary forces required for pressing the chain links. Moreover, the forced guidance operates very accurately and is exactly adjustable. The centering and joining forces can be produced in symmetry by means of a few components. The lever linkage can be changed very easily, so that apart from a control by the cam there is also a possibility of adjustment via the lever linkage or the complete exchange thereof.
Moreover, at least one lever section of the lever linkage may be designed to be adjustable in its length. It is thereby very easily possible to adjust the displacement path of a positioning mandrel or of a press block. Suitable adjusting devices permit a very high precision of the adjusting operation.
The whole lift mechanism is very simplified in its structure by the measure that an overload protection means of a compressible length is provided between slide bushing and cam and/or in the lever linkage. This overload protection means also compensates for the different lengths of the bolts or the thicknesses of the plates. This means that as soon as the necessary clamping force has been applied and e.g. a further force of displacement has been exerted by the cam on the slide-bushing, said bushing cannot move further and the length of path which is additionally produced by the cam is compensated by the overload protection means. Such a possibility of compensation may also be provided at any other desired and suitable place of the lifting mechanism. For instance, the positioning mandrels and press blocks themselves may comprise suitable compression means which are compressed as soon as a specific force has been reached. This is most advantageous in the case of the positioning mandrels because the centering force would increase very strongly as soon as both positioning mandrels had been brought into contact with the faces of the bolt.
To minimize the risk of deflection of the force-applying positioning mandrels, these may be guided in coaxial bores of the press block and may be movable relative to said block. This intimate arrangement of press block and positioning mandrel also ensures an exact alignment and positioning.
To join, in particular, an inner chain link, the positioning mandrels may be providedxe2x80x94in particular according to one embodimentxe2x80x94with a cylindrical attachment which can be moved in accurately fitting fashion into the bore of a hollow bolt of an inner chain link and which defines an annular abutment step relative to the adjoining portion of the positioning mandrel which can be brought into contact with a face of the hollow bolt. The attachment thus moves into the hollow bolt and ensures a coaxial alignment in said bolt, and the abutment steps of the opposite positioning mandrels will then ensure a symmetrical centering operation relative to the main chain axis. A deformation of the face portion by the annular abutment step is not possible because of the cylindrical attachment.
Furthermore, the positioning mandrel may comprise a centering portion which can removed into the opening of the plate and aligns said plate such that it is coaxial to the hollow bolt. Thus the plate is also aligned by the positioning mandrel in an exact manner before said plate is pushed onto the bolt. This, however, means that the supply means must just ensure a prepositioning operation within a wide range of tolerance and the centering operation proper is carried out by the positioning mandrel. The feeding operation is also facilitated by this measure to a considerable degree.
To compensate for diameter tolerances of the opening in the plate, one variant provides that the centering portion has a frustoconical shape. A centering operation is thereby carried out at any rate, i.e. independently of the size of the opening within the tolerance zone.
In addition it has been found that the whole joining operation can be made more precise and improved in that the centering portion and the abutment step are designed such that a slight joining lift can be carried out by the positioning mandrel for the attachment of the plate to the outer surface of the hollow bolt before the abutment step rests on the face of the hollow bolt. The position of the abutment step and the length of the centering portion as well as the shape thereof are adapted to the opening, in particular the thickness of the plate, such that a corresponding attaching operation is carried out. For instance, the plate can already be pushed with one quarter onto the bolt by said operation. Of course, it is also possible to move the positioning mandrel in parallel with the press block in said portion so that the actual application of the force is mainly carried out by the press block and the positioning mandrel just assumes the centering task during the attaching operation.
For a pressing operation over a surface of the plate that is as large as possible, the press blocks in one embodiment comprise a press block surface which surrounds the associated positioning mandrel and is substantially arranged in planar and vertical fashion relative to the mandrel axis and is displaceable relative to the positioning mandrel and presses the plate onto the outer surface of the hollow bolt. Tilting forces on the plate are avoided because the plate rests on the press block surface over a large surface thereof.
Furthermore, the upper and/or lower press blocks may comprise an extension which during the joining lift stops its movement and defines an exact joining distance of the press block surfaces relative to each other at the end of the joining lift. This makes above all sense when two plates are to be pushed onto the end portions of a bolt. The extension then defines the distance of the two plates relative to one another so that the plates, although they are pushed on in symmetrical fashion, leave an exactly defined distance thereinbetween. As for extensions which are arrested and stop their movement, an overload protection means may be of advantage.
For most of the chain links it is desirable to produce the same in a single joining operation. This fact is best taken into account according to one embodiment in that two upper positioning mandrels and two lower positioning mandrels are respectively arranged for forming a joining head in a jointly associated upper and lower press block. Such a joining head compensates for variations in the lengths of the two bolts. A compensation in the plates is not needed because it must be assumed that one plate does not vary in its thickness. This results in a very simple and compact construction which fully meets the demands made on the joining operation.
Advantageously, a supply means is provided which prepositions all elements of a chain link and supplies the same in a prealigned manner to a joining head. This is also novel because so far individual parts have most of the time been supplied separately and have then been connected at a corresponding joining place to the already prealigned components. The prepositioning and feeding operations for all elements at one time, i.e. all components are interconnected by a single joining operation, have so far not been carried out in the prior art with such a quality.
The device according to the invention is able to finish the chain link in a single joining operation. So far chain links have always been of a layered structure, with a joining lift being again performed in each layer. It has in particular been the objective of this invention to provide a method and a device in which a press fit can be accomplished in one single operation, even in the case of intermediate pin plates for duplex chains. A subsequent alignment or further displacement of the plates and bolts relative to one another, which would always entail a weakening of the press fit, is avoided. The device can operate at relatively low joining speeds because relatively small lifts have to be produced in the joining head, and nevertheless a higher output of chain links can be achieved because the joining steps have been reduced to a single joining operation. Moreover, this is a forced assembly in which all components are force-guided during the joining operation. The components can thus be aligned with one another in a very precise way.